package binary_search;

/**
 * 在排序数组中查找元素的第一个和最后一个位置
 * 二分查找！！！
 */
public class Demo20250329 {
    public int[] searchRange(int[] nums, int target) {
        int[] ret = new int[2];
        ret[0] = ret[1] = -1;
        // 处理边界情况
        if (nums.length == 0) {
            return ret;
        }

        // 1. 二分左端点
        int left = 0;
        int right = nums.length -1;
        while (left < right) {
            int mid = left + (right - left) / 2;
            if (nums[mid] < target) {
                left = mid + 1;
            } else {
                right = mid;
            }
        }
        // 判断是否有结果
        if (nums[left] != target) {
            return ret;
        } else {
            ret[0] = right;
        }

        // 2. 二分右端点
        left = 0;
        right = nums.length - 1;
        while (left < right) {
            int mid = left + (right - left + 1) / 2;
            if (nums[mid] <= target) {
                left = mid;
            } else {
                right = mid - 1;
            }
        }
        ret[1] = left;
        return ret;
    }
}
